Apple Calendar MCP demonstrates solid tool design with comprehensive parameter descriptions and clear naming conventions. All 10 tools follow verb_noun patterns (get_*, create_*, delete_*, search_*, update_*). Descriptions are detailed and contextual, averaging ~180 chars, well within the 10-1024 char baseline. Input schemas are present with type declarations and parameter descriptions. However, output schemas are not explicitly documented in the source code, responses are formatted as strings rather than structured JSON objects, which limits downstream tool chaining and forces LLMs to parse unstructured text. Error handling guidance is minimal. Tool composition is strong: tools are single-responsibility, and IDs flow correctly between tools (e.g., get_calendars returns calendar_id, which create_events accepts). Security is well-handled with no exposed credentials.

• Document output schemas for all tools. Specify that get_calendars returns an array of {calendar_id, name, writable, source, is_default, description, color} objects. Return structured JSON, not formatted strings.
• Add error recovery guidance to destructive tools: 'If calendar not found, call get_calendars() first to verify the ID. If read-only, the operation will fail, check the access level.'
• Implement a confirm_delete_calendar and confirm_delete_events tool, or add a 'dry_run' parameter to deletion tools to preview what will be deleted before committing.
• Refactor create_events, update_events, and delete_events to accept structured objects (arrays of event objects) instead of JSON strings. This enables schema validation and reduces serialization errors.
• Add limit and offset parameters to get_events and search_events. Document that results are capped at 100 items per call; use offset for pagination. Return a total_count field so LLMs know if more results exist.